Periodontal tissue is composed of alveolar bone, gingiva and periodontal ligament. Gingiva is a part of dental supporting apparatus in oral cavity, from which disease such as gingivitis is set off. As disease gets serious to spread deep into periodontal supporting apparatus, dental root and periodontal ligament attached on alveolar bone are destroyed, leading to the destruction of alveolar bone itself. As a result, periodontitis is developed.
Periodontal disease including gingivitis and periodontitis is characterized by inflammation in dental supporting apparatus caused by bacterial infection, which carries the symptoms of bleeding, periodontal pocket formation and alveolar bone destruction, leading to the loss of teeth. Periodontal disease progresses by following procedure: bacterial colony formation, invasion of bacteria into periodontal tissue and destruction of periodontal tissue. Particularly, oral bacteria form dental plaque due to poor oral hygiene, resulting in bleeding in gingiva and halitosis due to inflammation. When these symptoms are continued, a gap between teeth and gingiva becomes bigger, resulting in forming periodontal pocket, where bacteria causing periodontal diseases proliferate, resulting in periodontitis. As periodontitis progresses, gingival bleeding can be triggered by even weak stimulus such as tooth-brushing and becomes swollen, and sometimes it progresses to acute inflammation carrying great pain. The inflammation reduces the function of osteoblasts to form the bone with collagen, calcium and hydroxyapatite of phosphorus and increases the function of osteoclasts to destroy and resorb bone. As a result, alveolar bones are decreased in amount and further destroyed, leading to the loss of teeth. Osteoclasts are derived from monocytes/macrophages in bone marrow. Monocyte precursor cells circulate through blood, proliferate and are fused in endosteum to form polykaryocytes. Osteoclasts characteristically contain TRAP (tartrate-resistant acid phosphatase) which is an acid phosphatase having tartrate-resistance and used as a cytochemical marker enzyme to distinguish osteoclasts from other bone tissue cells [Minkin, C., Calcif. Tissue Int., 34:285-290, 1982].
There is variety of causes of periodontal disease. For example, the deposit of dental plaque in periodontal pocket provides a habitat for anaerobic Gram (−) bacteria around, leading to the proliferation of those bacteria deep in periodontal pocket. Toxin of the proliferated anaerobic Gram (−) bacteria and other products thereby might directly destroy the tissues or stimulate immune system. Accordingly, periodontal tissue is destroyed by various related immune responses and inflammation is caused. As a defense mechanism against such inflammation, polymorphonuclear leukocytes and systemic immune response are required. That is, as a result of anaerobic Gram (−) bacteria metabolism, the levels of highly toxic hydrogen sulfide, ammonia and amine are increased in periodontal tissue and at the same time the tissue is destroyed directly by endotoxin such as lipopolysaccharide, a cell wall component, or inflammation in gingiva is developed by extracellular active oxygen, prostaglandin, leukotrien, histamine and interleukin via actions of humoral and cell-mediated immune systems stimulated by such toxins. Bacteria and leukocytes induce the secretion of collagenase, by which collagen, a matrix of periodontal tissue, is decomposed, resulting in recession of gum. If left untreated, it progresses to periodontal disease. Therefore, bactericidal activity and bacteriostatic action against anaerobic Gram (−) bacteria, a fundamental causing factor, elimination of toxins and recovery of damaged periodontal tissue are key points for prevention and treatment of periodontal disease.
For treatment of periodontal disease, in addition to emphasizing on oral hygiene of a patient, non-surgical or surgical scaling, root planing, curettage and periodontal tissue regeneration using new attachment have been performed. However, these surgical treatments are limited to the treatment of progressed diseases only, not effective for prevention of disease, and ask patients to visit a dental clinic necessarily. Most periodontal diseases progress to chronic diseases without early treatment. Supplementary treatment such as administration of antibiotics and local slow-releasing agents has been performed with the fundamental treatment, but it has problems of side effects caused by medicine administered to whole body, which means untargeted areas are also affected, and generating periodontal disease bacteria having a resistance against antibiotics (in fact, periodontal disease bacteria showing antibiotics resistance have been isolated).
To overcome the limited application of surgical treatments and side effects of antibiotics, a novel agent having activity of recovering destroyed and lost periodontal tissue is required for prevention and treatment of periodontal disease.
According to Melcher, an origin of a cell involved in regeneration of periodontal tissue is a key factor affecting the regeneration. For example, if a cell originated from bone is involved, synostosis occurs. If connective tissue originated cells (Ex. gingival fibroblasts) are involved, dental root resorption occurs. If epithelial tissue derived cells are involved, long epithelial attachment is generated, suggesting that regeneration of periodontal tissue is unsatisfactory. If periodontal ligament cell derived cells are involved, most desirable regeneration of periodontal tissue is expected.
Based on the fact that activation of CD4+ T cells inducing secretion of inflammatory cytokines (TNF-, IFN-, GM-CSF, IL-2, IL-6) stimulates the expression of osteoprotegerin ligand on the surfaces of osteoblasts to cause osteoclastogenesis which plays a crucial role in bone destruction, the present inventors fully accept the necessity to develop a new agent having activities of preventing alveolar bone from destruction by suppressing inflammation caused by cytokine secretion, enhancing the proliferation and differentiation of osteoblasts and reducing formation and activation of osteoclasts to protect alveolar bone but not affecting the proliferation of gingival fibroblasts and periodontal ligament cells [Kong, Y. Y. et al., Nature 402:304-309, 1999].
Thus, it is confirmed that the best way to promote regeneration of periodontal tissue is to promote the growth of periodontal ligament cells and to maintain the normal growth of gingival fibroblasts. If it is not possible to satisfy the above two conditions, it is preferred for an agent at least not to affect the growths of the two types of cells, especially with preventing soft tissue alternative healing by gingival fibroblast proliferation.
Therefore, the present inventors have studied on herbal medicines to examine the possibility of being an agent to inhibit cytokine secretion, promote the proliferation and differentiation of osteoblasts, and reduce formation and activation of osteoclasts to protect alveolar bone from being destroyed. As a result, the present inventors completed this invention by confirming that a herbal mixture extract of Pleurotus eryngii, Acanthopanacis Cortex and Notoginseng Radix can inhibit inflammation carried by periodontal disease but not affect the normal growths of gingival fibroblasts and periodontal ligament cells, so that the extract can be effectively used for prevention and treatment of periodontal disease.